Filling the Eastern Himalayan Gap: Structural Architecture and Kinematics of the Himalayan Orogen in Bhutan

填补喜马拉雅东部缺口：不丹喜马拉雅造山带的结构建筑和运动学

• 批准号: 1158741
• 负责人: Nadine McQuarrie
• 金额: $ 4.81万
• 依托单位: University of Pittsburgh
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-07-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1158741&HistoricalAwards=false
• 关键词: Filling; Eastern; Himalayan; Gap; Structural

The 2,400 km long Himalayan fold and thrust belt extends from the Nanga Parbat massif in northern Pakistan to the Namche Barwa syntaxis in eastern Tibet. There are only a handful of estimates that quantify the magnitude and geometry of shortening along this fold and thrust belt with no such estimates in the eastern portion of the range, a region characterized by fundamental changes in the geomorphic, geometric, and lithologic expression of the belt. In particular, the lack of information on the magnitude, style, and timing of shortening in the Lower Himalayan Series, a thick succession of early to middle Proterozoic-Paleozoic greenschist facies to unmetamorphosed metasedimentary rocks within the belt, inhibits understanding of the development of the Himalayan orogenic belt. The goal of this project is to determine the geometry, amount of shortening, and kinematic history of deformation in the Lower Himalayan Series as exposed in the Kingdom of Bhutan. Toward this end, a team of scientists from Princeton University and Bhutan are mapping the Lesser Himalayan Sequence from the Main Central Thrust to the Main Frontal Thrust. These field relationships and new U-Pb ages of detrital zircons are used to develop a regional stratigraphic framework. Balanced crustal-scale structural cross-sections are restored sequentially when combined with new thermochronologic and geochronologic ages in order to elucidate regional cooling patterns and to constrain timing of fault motion. These results allow evaluation of how deformation is partitioned in space and time, prediction of minimum shortening estimates, determination of minimum lateral and vertical erosion estimates compatible with both the balanced section and thermochronometers, and in the end, comparison of the timing and magnitude of deformation and exhumation between the Lesser and Greater Himalayan Series.The Himalayan mountain range is a consequence of the ongoing collision between India and Asia. During collision, the sedimentary cover that had blanketed northern India for the last 1.8 billion years became detached from the underlying basement. This deformed sedimentary cover, and the structures that developed within it, record the deformation history of the collision. Although it is one of the world's most famous mountain ranges, only a handful of estimates quantify this deformation and there are no such estimates for the eastern portion of the mountain belt. This study of the deformed rocks in the Kingdom of Bhutan will provide new estimates for this poorly understood portion of the range and, when compared to estimates for other portions of the Himalayan Range, will lead to a better understanding of the development of collisional mountain belts. The project fosters scientific collaboration between scientists from Bhutan and the United States and helps to build scientific infrastructure in Bhutan by training of Bhutanese students and an improved knowledge of the geology of the country, which in turn is important for understanding earthquake hazards and natural resources.

喜马拉雅褶皱冲断带长2,400公里，从巴基斯坦北方的南迦帕尔巴特峰一直延伸到西藏东部的南迦巴瓦构造结。只有少数的估计，量化的幅度和几何缩短沿着这个褶皱和冲断带，没有这样的估计在东部的范围，一个地区的特点是根本的变化，在地貌，几何和岩性的表达带。特别是，缺乏信息的规模，风格和缩短的时间在下喜马拉雅系列，一个厚厚的继承早期到中期元古界-古生代绿片岩相带内未变质的变质沉积岩，抑制喜马拉雅造山带的发展的理解。该项目的目标是确定不丹王国暴露的下喜马拉雅系列的几何形状、缩短量和变形的运动学历史。为此，来自普林斯顿大学和不丹的一组科学家正在绘制从主中央冲断层到主锋面冲断层的小喜马拉雅序列。这些现场关系和新的碎屑锆石U-Pb年龄被用来制定一个区域地层格架。平衡的地壳规模的结构截面恢复顺序时，结合新的热年代学和地质年代学年龄，以阐明区域冷却模式和限制断层运动的时间。这些结果允许评估变形如何在空间和时间上划分，预测最小缩短估计，确定与平衡截面和热计时器兼容的最小横向和垂直侵蚀估计，最后，小喜马拉雅系列和大喜马拉雅系列之间变形和折返的时间和幅度的比较。喜马拉雅山脉是两个正在进行的碰撞的结果，印度和亚洲。在碰撞过程中，覆盖印度北方达18亿年之久的沉积物覆盖层与下面的基底分离。这种变形的沉积盖层以及在其中形成的构造记录了碰撞的变形历史。虽然它是世界上最著名的山脉之一，但只有少数估计量化了这种变形，并且没有对山脉东部的估计。这项对不丹王国变形岩石的研究将为喜马拉雅山脉这一知之甚少的部分提供新的估计，与喜马拉雅山脉其他部分的估计相比，将有助于更好地了解碰撞山脉的发展。该项目促进了不丹和美国科学家之间的科学合作，并通过培训不丹学生和增进对该国地质的了解，帮助建立不丹的科学基础设施，这反过来对了解地震灾害和自然资源很重要。